Chapter 2. Univariate Volatility Modeling (in R/Python)


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Listing 2.1/2.2: ARCH and GARCH estimation in R
Last updated July 2020

library(rugarch)
p = read.csv('index.csv')
## We multiply returns by 100 and de-mean them
y=diff(log(p$Index))*100
y=y-mean(y)
## GARCH(1,1)
spec1 = ugarchspec(variance.model = list( garchOrder = c(1, 1)),
 mean.model = list( armaOrder = c(0,0),include.mean = FALSE))
res1 = ugarchfit(spec = spec1, data = y)
## ARCH(1)
spec2 = ugarchspec(variance.model = list( garchOrder = c(1, 0)),
 mean.model = list( armaOrder = c(0,0),include.mean = FALSE))
res2 = ugarchfit(spec = spec2, data = y)
##Ā tGARCH(1,1)
spec3 = ugarchspec(variance.model = list( garchOrder = c(1, 1)),
 mean.model = list( armaOrder = c(0,0),include.mean = FALSE),
 distribution.model = "std")
res3 = ugarchfit(spec = spec3, data = y)
## plot(res) shows various graphical analysis, works in command line
		
Listing 2.1/2.2: ARCH and GARCH estimation in Python
Last updated July 2020

import numpy as np
p = np.loadtxt('index.csv', delimiter = ',', skiprows = 1)
y = np.diff(np.log(p), n=1, axis=0)*100
y = y-np.mean(y)
from arch import arch_model
## using Kevin Sheppard's ARCH package for Python
## ARCH(1)
am = arch_model(y, mean = 'Zero', vol='Garch', p=1, o=0, q=0, dist='Normal')
arch1 = am.fit(update_freq=5, disp = "off")
## ARCH(4)
am = arch_model(y, mean = 'Zero', vol='Garch', p=4, o=0, q=0, dist='Normal')
arch4 = am.fit(update_freq=5, disp = "off")
## GARCH(4,1)
am = arch_model(y, mean = 'Zero', vol='Garch', p=4, o=0, q=1, dist='Normal')
garch4_1 = am.fit(update_freq=5, disp = "off")
## GARCH(1,1)
am = arch_model(y, mean = 'Zero', vol='Garch', p=1, o=0, q=1, dist='Normal')
garch1_1 = am.fit(update_freq=5, disp = "off")
## t-GARCH(1,1)
am = arch_model(y, mean = 'Zero', vol='Garch', p=1, o=0, q=1, dist='StudentsT')
tgarch1_1 = am.fit(update_freq=5, disp = "off")
print("ARCH(1) model:", "\n", arch1.summary(), "\n")
print("ARCH(4) model:", "\n", arch4.summary(), "\n")
print("GARCH(4,1) model:", "\n", garch4_1.summary(), "\n")
print("GARCH(1,1) model:", "\n", garch1_1.summary(), "\n")
print("tGARCH(1,1) model:", "\n", tgarch1_1.summary(), "\n")
		

Listing 2.3/2.4: Advanced ARCH and GARCH estimation in R
Last updated July 2020

## Normal APARCH(1,1)
spec4 = ugarchspec(variance.model = list(model="apARCH", garchOrder = c(1, 1)),
 mean.model = list( armaOrder = c(0,0),include.mean = FALSE))
res4 = ugarchfit(spec = spec4, data = y)
## show(res4)
## Normal APARCH(1,1) with fixed delta
spec5 = ugarchspec(variance.model = list(model="apARCH", garchOrder = c(1, 1)),
 mean.model = list( armaOrder = c(0,0),include.mean = FALSE), fixed.pars=list(delta=2))
res5 = ugarchfit(spec = spec5, data = y)
show(res5)
		
Listing 2.3/2.4: Advanced ARCH and GARCH estimation in Python
Last updated July 2020

## Leverage effects
am = arch_model(y, mean = 'Zero', vol='Garch', p=1, o=1, q=1, dist='Normal')
leverage_garch1_1 = am.fit(update_freq=5, disp = "off")
## Power models, delta = 1
am = arch_model(y, mean = 'Zero', vol='Garch', p=1, o=0, q=1, dist='Normal', power = 1.0)
power_garch1_1 = am.fit(update_freq=5, disp = "off")
print("Leverage effects:", "\n", leverage_garch1_1.summary(), "\n")
print("Power model:", "\n", power_garch1_1.summary(), "\n")